1. Field of the Invention
The present invention relates to an integrated circuit device having multilayer structure, and more particularly, it relates to the structure of an integrated circuit device comprising a substrate and an integrated circuit formed thereon, which can prevent leakage of secret matters due to difficulty in analysis of formation, arrangement, etc., of the integrated circuit.
2. Description of the Background Art
FIG. 4 is a typical sectional view showing an example of a conventional semiconductor integrated circuit device.
Referring to FIG. 4, a semiconductor substrate 1 of single-crystalline silicon or the like is provided on one major surface thereof with an integrated circuit 2 which has electronic devices such as transistors and resistors. The integrated circuit 2 is connected to an external circuit (not shown) through bonding pads 3 which are provided by evaporating aluminum or the like on the substrate 1. A protective film 4 of resin or the like is formed on the surface of the integrated circuit 2.
In such an integrated circuit device, the integrated circuit 2 of high density must be formed on the substrate 1, the area of which is limited. Therefore, much labor and cost are required in order to increase the degree of integration by improving formation of the integrated circuit 2 and device arrangement. Thus, formation, arrangement etc. of such an integrated circuit must be kept secret for each manufacturer.
In the conventional integrated circuit device, however, only the protective film 4 is provided on the integrated circuit 2. Therefore, if the protective film 4 is highly transparent, the integrated circuit 2 formed on the substrate 1 can be directly observed in an enlarged manner through a microscope or the like. Even if the protective film 4 is made of opaque resin, the integrated circuit 2 can be observed similarly to the above by removing the protective film 4 by a method such as etching.
Thus, secret matters such as formation and arrangement of the integrated circuit 2 provided on the substrate 1 are easily analyzed by a third party or the like, to spoil efforts and interests of those rendering services to development of such technique.